Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Mar. 31, 2018	$ 689,524	$ 444	$ (67,078)	$ 619,905	$ 140,457	$ (4,204)
Beginning Balance (in shares) at Mar. 31, 2018		44,375,337	1,725,312
Restricted stock units issued		$ 4		(4)
Restricted stock units issued (in shares)		384,887
Stock options exercised	5,798	$ 3		5,795
Stock options exercised (in shares)		282,368
Stock issued to directors	33			33
Stock issued to directors (in shares)		80
Return of common stock to pay withholding taxes on restricted stock	(67,598)	$ (2)	$ (67,596)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(166,401)	166,401
Stock compensation expense	12,245			12,245
Other comprehensive income (loss)	(6,709)					(6,709)
Net income	90,066				90,066
Ending Balance at Jun. 30, 2018	723,359	$ 449	$ (134,674)	637,974	230,523	(10,913)
Ending Balance (in shares) at Jun. 30, 2018		44,876,271	1,891,713
Beginning Balance at Mar. 31, 2019	$ 936,890	$ 451	$ (138,852)	690,507	399,473	(14,689)
Beginning Balance (in shares) at Mar. 31, 2019	45,122,985	45,122,985	1,903,241
Restricted stock units issued		$ 4		(4)
Restricted stock units issued (in shares)		373,430
Stock options exercised	$ 1,261	$ 1		1,260
Stock options exercised (in shares)	36,000	36,289
Return of common stock to pay withholding taxes on restricted stock	$ (40,536)	$ (2)	$ (40,534)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(158,426)	158,426
Stock compensation expense	13,121			13,121
Other comprehensive income (loss)	2,934					2,934
Net income	88,923				88,923
Ending Balance at Jun. 30, 2019	$ 1,002,593	$ 454	$ (179,386)	$ 704,884	$ 488,396	$ (11,755)
Ending Balance (in shares) at Jun. 30, 2019	45,374,278	45,374,278	2,061,667